Spin-Filter Effect Induced by Magnetic Edge States of Zigzag Carbon Nanotube

Spin-filter effect is predicted in a weak coupled junction composed of a nonmagnetic metal electrode and a zigzag carbon nanotube. This effect is induced by the magnetic edge states of the nanotube, and can produce spin-polarized current in the absence of an external magnetic field. We find that the spin polarization of the current changes its sign at the half-fillingpoint of the nanotube, thus electric field control of spin transport can be realized. Furthermore, we find the coupling strength of the junction may cause a magnetic transition on the edge of the nanotube.